High temperature alloys



y 12, 1966 M. N. ORNITZ ETAL 3,260,594

HIGH TEMPERATURE ALLOYS Filed Jan. 11, 1965 4 Sheets-Sheet 1 Fig. l.

Rqdluns/hr x I6 04 4 O1 Tungsten Fig. 2.

Rudions/hr x IO N 01 Q o o Tungsten INVENTORS Martin N. Ornitz 8 July 12, 1966 Filed Jan. 11. 1965 M. N. ORNlTZ ETAL HIGH TEMPERATURE ALLOYS Fig. 4.

4 Sheets-Sheet 5 g 70 2 a a: 60 l9 1 X 5 4O so 6 2O l0 /I .IO .20 .30 .40 .50 .60 .70 .80 .90 L00 Carbon Fig. 5.

l5 2' (0 C O 3 tho 9 a A g -c7 F) C3 Manganese INVENTORS Martin N. Ornirz 8 Ray H. English July 12, 1966 M. N. ORNlTZ ETAL 3,260,594

HIGH TEMPERATURE ALLOYS Filed Jan. 11. 1965 4 Sheets-Sheet 4 Fig.6.

Creep Ruie Rudions/hr.

IO l2 l4 16 I8 20 22 24 Chromium INVENTORS Martin N. Omitz 8| Roy H. English United States Patent 3,260,594 HIGH TEMPERATURE ALLOYS Martin N. Ornitz, Wilkinsburg, and Ray H. English,

McCandless Township, Allegheny County, Pa., assignors to Blaw-Knox Company, Pittsburgh, Pa., a corporation of Delaware Filed Jan. 11, 1965, Ser. No. 425,687 Claims. (Cl. 75-128) used for applications in this temperature range have not i been satisfactory for most uses because of the high rate of creep, corrosion and lack of strength at temperatures at or about 1600 F. to 2200 F.

'We have discovered an alloy composition having high strength and low creep characteristics coupled with corrosion resistance and high resistance to thermal shock at temperatures of about 1600 F. to 2200" F. The surprising characteristics of this alloy appear to be particularly dependent upon the control of carbon, manganese and tungsten within a critical nickel-chromium iron base analysis. The broad composition range of the alloy of this invntion lies within the following limits:

Carbon About 0.3% to about 0.9%. Chromium About 17% to about 30%. Nickel About 15% to about 35%. Manganese About 0.8% to about 4%. Silicon About 0.9% to about 3.5%. Tungsten About 0.3% to about 5%. Balance Iron with residual impurities in ordinary amounts.

While the foregoing broad alloy composition will give generally satisfactory results at or above 1800 R, we have found that for continued service above about 2100 F. the following narrower range of composition should be observed:

Carbon About 0.35% to about 0.75%. Chromium About 20% to about 30%. Nickel About 30% to about 35%. Manganese About 1.2% to about 2.4%. Silicon About 1.2% to about 2.5 Tungsten About 1.75% to about 5%. Balance Iron with residual impurities in ordinary amounts.

A single preferred composition would be:

Carbon About 0.4%.

Chromium About 23%.

Nickel About 30%.

Manganese About 1.5%.

Silicon About 2%.

Tungsten About 1.75%.

Balance Iron with residual impurities in ordinary amounts.

We have found that the foregoing ranges are critical if the desired high strength, low creep, corrosion resistance and resistance to thermal shock are to be achieved. We have found that small amounts of columbium in the range 0.15% to 1% may be beneficial and will impart improvement in creep characteristics. However, the presence of columbium in excess of 1% markedly decreases the hot strength of the alloy. This is a peculiar phenomenon which is unexplainable so far as we are concerned.

We have also found that above about 2200 F. the chromium content must be 20% or higher to avoid catastrophic oxidation. The lower limit of chromium is critical if oxidation resistance and high creep at temperatures above 1800 F. and particularly above 2000 F. are to be attained.

The unusual properties of our alloy and the criticality of the composition are perhaps best illustrated by comparison of the following test results and examples.

EXAMPLE I One-hunderd hour oxidation tests of an alloy which has been used extensively at these temperatures prior to the present invention for high temperature use, and of the present alloy gave the following results:

Table 1 C M11 Si Ni Cr Alloy of invention 0.37 1.46 Bal.

1.90 24.5 25.7 Conventional prior alloy- 1.70 33.4 17.8

Table 2. hour oxidation in air at 2200" F.

Alloy of invention 0.043 inch penetration/ year.

Conventional prior alloy 0.117 inch penetration/year (catastrophic oxidation on edges).

EXAMPLE II Table 3 Heat 0 Mn Si Ni Or W Rate,

EXAMPLE III Tests were made to determine the creep rate of the alloys of this invention with alloys outside the invention at a temperature of 2000 F. and a loading of 1500 p.s.i. The results of these tests appear in Table 4 below and FIGURE 2 of the accompanying drawings in which creep rate is plotted against tungsten content.

Table 4 stage tests at 2250 F. 110 F. for 50 hours. The compositions were as follows: Heat Mn 31 Ni Cr W 1 1 3 Table 6 5 .40 1.49 1.47 24.0 23.9 11.4 HeatI C I I S1 Ni W .31 1.31 1.65 2 4.2 33.2 3.3 .5 1.99 1.99 .36 1.04 1.69 23.3 21.6 10.0 .43 1.10 1.62 24.0 22.0 9.5 045 243 .33 1.12 1.60 24.1 21.6 9.0 .39 1.02 1.54 23.7 22.0 9.5 1

42 111 152 246 235 100 0.46 1.52 2.16 24.3 20.1 1.20 L05 L48 2% 220 24.0 0.67 1.56 1.33 25.5 23.1 1.63 .35 1.33 1.33 24.6 22.4 23.0 .43 1.04 1.52 24.6 21.3 3.7 1&8 The oxidation test results are tabulated in Table 7 15 herein below:

Table 7 FIRST STAGE Heat N0 4653 I 4659 I 4660 I 4661 I 4662 4663 Initial wt.,gr 163.4763 167.6905 170.2032 166.9733 163.7276 171.0510 Fmalwt.,gr 143.6737 162.3314 169.9572 166.6234 163.4054 170.7605 Awt 19.3031 4.3091 0.2460 0.3504 0.3222 0.2905 Surface area, m. 2 6. 932 6. 932 7.045 6. 962 7. 056 7. 107 Rate, gr./1n. hr 0.0235 0.00693 0.00035 0.00050 0.00046 0.00041 SECOND STAGE 168. 0323 169. 9667 Catastrophic oxidation 0. 3731 0. 7938 0.0011 0.0022

In FIGURE 3A there is illustrated the curve of stress rupture (solid line) and the curve of creep rate in percent deflection (chain line) at 1800 F. for an alloy of the composition C .42 Ni 256 Mn 1.46 Cr 227 S1 185 W 142 In FIGURE 3B there is illustrated the curve of stress rupture (solid line) and the curve of creep rate in percent deflection (chain line) at 2000 F. for the same alloy.

Variations in carbon are plotted against rate of creep in FIGURE 4 and variations of manganese are plotted against rate of creep in FIGURE 5 all within the matrix of this invention.

EXAMPLE IV Tests were made to compare alloys according to our invention with prior art alloys such as those specifically set out in Hadfield Patent 1,528,478 and to show the critical nature of the chromium limits. A series of alloys were made varying the chromium content and cantilever creep data at 2000 F. and 1500 p.s.i. were determined. The compositions of the several alloys and the creep data The very sharp break in the curve of creep rate vs.

chromium at about 17% chromium is illustrated in FIG- URE 6.

EXAMPLE V Another series of tests were made to compare prior art alloys with the alloys 'of this invention in oxidation tests at 2200 F. and at 2250 F. The first stage tests were run for 100 hours at 2200 F. :10 F. and the second The foregoing tests show the criticality of the chromium at about 17% in withstanding oxidation at 2200 F. and the criticality of 20% chromium at 2250 F. in avoiding catastrophic oxidation.

The foregoing tables and accompanying drawings clearly illustrate the criticality of the composition of this alloy and the very significantly improved creep and corrosion resistant properties.

Experimental heat treating trays were made of the preferred alloy composition of this invention. These trays were used for four months for carrying parts to be hardened at temperatures of 1600 to 1750 F., carburizing and carbonitriding. The trays were cyclically heated to the temperature and then put through an oil quench and draw. At the end of the four month period all trays were in excellent condition. This experience illustrates the excellent resistance to thermal shock of the alloy of the invention.

While we have described certain preferred embodiments of our invention in the foregoing specification, it will be understood that the invention may be otherwise embodied within the scope of the following claims.

We claim:

1. A low creep, high strength alloy resistant to corrosion and thermal shock at elevated temperatures having stress rupture characteristics at 4000 p.s.i. and 1800 F. of at least 400 hours and at 2000 F. and 2000 p.s.i. of at least hours comprising about 0.3% to 0.9% carbon, about 20% to 30% chromium, about 15% to 35% nickel, about 0.8% to 4% manganese, about 0.9% to 3.5% silicon, about 0.3% to 5% tungsten and the balance iron with residual impurities in ordinary amounts.

2. A low creep, high strength alloy resistant to corrosion and thermal shock at elevated temperatures having stress rupture characteristics at 4000 p.s.i. and 1800 F. of at least 400 hours and at 2000 F. and 2000 p.s.i.

of at least 100 hours comprising about 0.35% to 0.75% carbon, about 20% to 30% chromium, about 30% to 35% nickel, about 1.2% to 2.4% manganese, about 1. 2% to 2.5% silicon, about 1.75% to 5% tungsten and the balance iron with residual impurities in ordinary amounts.

3. A low creep, high strength alloy resistant to corrosion and thermal shock at temperatures of 1800 F. to 2200 F. comprising about 0.3% to 0.9% carbon, about 17% to 30% chromium, about 15 to 35% nickel,

about 0.8% to 4% manganese, about 0.9% to 3.5% silicon, about 0.3% to 5% tungsten and the balance iron with residual impurities in ordinary amounts.

4. A low creep, high strength alloy resistant to corrosion and thermal shock at temperatures of 1800 F. Ito 2200 F. comprising about 0.35% to 0.75% carbon, about to chromium, about 30% to nickel, about 1.2% to 2.4% manganese, about 1.2% to 2.5% silicon, about 1.75% to 5% tungsten and the balance iron with residual impurities in ordinary amounts.

5. A loW creep, high strength alloy resistant to corrosion and thermal shock at temperatures of 1600 F. to 2200 F. comprising about 0.4% carbon, about 23% chromium, about 30% nickel, about 1.5% manganese, about 2% silicon, about 1.75 tungsten and the balance iron With residual impurities in ordinary amounts.

References Cited by the Examiner UNITED STATES PATENTS 1,528,478 3/1925 Hadfield 128 HYLAND BIZOT, Primary Examiner.

DAVID L. RECK, Examiner.

P. WEINSTEIN, Assistant Examiner. 

1. A LOW CREEP, HIGH STRENGTH ALLOY RESISTANT TO CORROSION AND THERMAL SHOCK AT ELEVATED TEMPERATURES HAVING STRESS RUPTURE CHARACTERISTICS AT 4000 P.S.I. AND 1800* F. OF AT LEAST 400 HOURS AND AT 2000*F. AND 2000 P.S.I. OF AT LEAST 100 HOURS COMPRISING ABOUT 0.3% TO 0.9% CARBON, ABOUT 20% TO 30% CHROMIUM, ABOUT 15% TO 35% NICKEL, ABOUT 0.8% TO 4% MANGANESE, ABOUT 0.9% TO 3.5% SILICON, ABOUT 0.3% TO 5% TUNGSTEN AND THE BALANCE IRON WITH RESIDUAL IMPURITIES IN ORDINARY AMOUNTS. 